It has long been established that the continuous monitoring of pH in the distal esophagus over extended periods of time (i.e., of at least 24 hours) provides data useful in the evaluation of gastroesophageal disease. The earlier devices developed to perform such monitoring employed an electrode inserted through the nasal passage into the esophagus, a reference electrode in contact with the patient's skin, an electrical shock isolation module through which the signal from the electrodes and the patient were electrically isolated from monitoring instruments, and a pH meter and recording apparatus receiving, displaying and recording the isolated signal.
These devices effectively tether the patient to the pH meter and recorder because the electrodes and pH meter must be wired together by electrical conductors. With such a restricted range of movement, the patient's activities must be similarly circumscribed, resulting in data, generally known as a reflux pattern, that is not usually a true reflection of what generally occurs during the patient's ordinary activities.
More recently another device has been employed in the monitoring of pH in the distal esophagus. This device envisions the patient swallowing a capsule containing both a pH electrode and a micro-miniature radio transmitter having its own self-contained power supply adequate for up to an eight hour monitoring period. The capsule would be positioned and secured in the gastric pouch at the esophagogastric junction by string tied to the capsule and taped to the incisor teeth. A belt containing a plurality of pick-up antennas was wrapped around the patient's waist and electrically connected via conductors to the necessary instrumentation. In this manner the pH data could be radiotelemetered to the pick-up antennas and associated instruments.
For several reasons this more recent device is at least as deleterious as those which preceded it. The patient is subjected to even greater discomfort as a result of utilization of the capsule system. The antenna belt, which must be physically connected to the instrumentation, subjects the patient to at least as much interference to and limitation upon his zone of movement as that of the earlier devices, and still creates a possibility of electrical shock. The limited power capacity of the capsule's self-contained power supply results in monitoring times restricted to periods too short to provide an adequate sampling of the patient's reflux pattern. Moreover, the necessity for highly specialized equipment makes the system relatively expensive to purchase and operate, requiring the constant supervision of trained personnel, which supervision may only be provided by hospitalization for the duration of the study.